The FOH Magazine JK Series Review


 Written by George Petersen

KV2 Audio JK Series Direct Boxes - JK 1

(August 4, 2012)  For the past decade, KV2 Audio has built a reputation for creating rugged, great-sounding pro audio gear. Founder George “Jiri” Krampera always made products with novel, innovative approaches. So when KV2 announced its JK Series direct boxes, I was anxious to check these out.

Does the world really need more direct boxes? Well, having used the JK Series, I can answer in the affirmative. The line has four models, the passive JK P ($295 MSRP) and three active variants: the JK 1 (single-channel, $295 MSRP), the JK 2 (dual-channel, $390 MSRP) and the JK A (for use with acoustic instruments, $329 MSRP). All feature rugged construction with quality European parts. They are hand-built in the Czech Republic and come with a five-year warranty.

Krampera is known for creating tools with uncompromised performance, and the JK series are no exception. For clarity and ultra-low distortion, the active models utilize a switching power supply for 20 volt peak power on the internal rails. This enables each to provide a low, 50-ohm impedance line-level output with line driver capability for extremely long cable runs.

The active units are line-out only and operate solely on phantom power (48 to 56 VDC with an 8 mA draw) to avoid the compromise of 9VDC powering. If you need a battery-operated box, you’ll have to look elsewhere, or use the JK P passive unit. The line output is a godsend, especially snaking over long runs, whether from an instrument, keyboard, mic-level output from a wireless receiver or the unbalanced feed from a PC, iPod/iPad, CD/DVD player, etc.

JK 1

This active DI box/line driver has two 1/4-inch inputs with a switch to select parallel (for using the other jack to feed an amp, etc.), a “Mix” setting for combining both jacks to mono, or parallel with a -15dB input pad. It also has switches for phase reverse, ground lift and selectable 80/160 Hz LF rolloff. There’s also an inline 20 Hz highpass filter to remove unwanted low-end crud.

KV2 Audio JK Series Direct Boxes - JK 2JK 2

Each channel of the JK 2 stereo active DI box/line driver has 1/4-inch and RCA inputs with parallel 1/4-inch outs. Switches are provided for ground lift, input pad (0/-12/-24 dB) and phase reverse. Seems simple enough, but KV2 adds a few bonus extras. The phase switch also has an “Off” position that mutes either input, a useful touch for checking the left or right channels during setups. The ground lift adds an “RC” setting — beyond the ground and lift positions — that routes the input/output ground through a parallel resistor/capacitor network to suppress RFI or static conditions. The JK 2 can be powered via phantom from either channel, yet performance in stereo is significantly improved when phantom is applied to both channels.

KV2 Audio JK Series Direct Boxes - JK AJK A

The last active DI box/line driver in the series, the JK A, is designed for acoustic instrument pickups and is ideal for high-impedance (1 Mohm) piezo transducers or active electronics with input peaks as high as 7 volts. Phase reverse and +10dB gain boost switches (for low output pickups) are standard. But in Krampera tradition, the JK A adds a twist. Rather than simply paralleling the second 1/4-inch jack for an amp feed, that jack is taken after the amplifier and is transformer isolated from the 50-ohm, line level XLR out, with the ground on the 1/4-inch output jack routed via an RC network. A built-in notch filter is sweepable from 75 to 1.6k Hz with a switchable -6/-12 dB cut. The latter proved ideal for dealing with feedback, especially with large body acoustic guitars. With the filter’s fixed, ultra-narrow Q of 12, I was able to get in, deal with the resonant frequency problem and leave no audible artifacts.

KV2 Audio JK Series Direct Boxes - JK PJK P

Most passive direct boxes simply insert a transformer between the input and output jacks, but as a Krampera design, the JK P passive DI adds a few new tricks, beyond its three-position ground lift with RC setting. Inputs are a Neutrik Combo XLR/TRS, paralleled to a 1/4-inch TRS jack. The transformer provides switchable windings in 1:2 or 1:4 ratios. The unit needs no phantom power to operate. However, a switchable “phantom through” function can route phantom power from the console directly to t he input XLR. This way, the JK P can also be used with condenser — or dynamic — mics, either as a splitter to both of its XLR outputs or as an in-line transformer to lower the impedance of the mic’s output for long cable runs. This also offers more sonic options to choose from, such as routing a dynamic mic using the 1:2 setting for a rounder, smoother sound, yet at the same time having the flexibility of handling line, instrument or unbalanced consumer-level input sources.

The Bottom Line

Combining low distortion and high-headroom performance with innovative feature sets, KV2 Audio’s JK series are worth checking out. Anyone who thinks direct boxes are utilitarian and boring should be prepared to be surprised.

For more on the JK Series of utility boxes, please contact LIFT Distribution at: 

, or (888) 954-3828